A performance and lecture by composer and bassist Mark Dresser, recorded on April 15, 2008, at the Marsh, in San Francisco, as part of the Improv:21 series sponsored by ROVA Arts. After a brief introduction by Derk Richardson, Dresser takes the stage and performs a lengthy improvisation, before launching into what is no less than a master class on extended playing techniques, intervals, harmonics, and the creative uses of amplification. Dresser, who was born in Los Angeles, studied music at U. C. San Diego, and has spent a considerable amount of time playing with a variety of world class musicians in New York City and elsewhere, begins by describing how he was first drawn to music through the free and expressive playing of Jimi Hendrix and Charlie Mingus, among others. Further association and study with such teachers as Bertram Turetzky, Franco Petracchi, and Robert Erickson, gave Dresser an appreciation of both traditional and contemporary performance practices. However it wasn’t until he really began to improvise and then go back to transcribe and analyze his playing, that he really began to understand the variety of sounds that could be “excavated” from his chosen instrument. Through a thorough investigation of scales and intervals, different tunings, overtones and harmonics, systems for guided improvisation (such as Walter Thompson’s Soundpainting), and the use of electronic pickups placed in unorthodox positions, including on the bow, Dresser has managed to map out an impressive number of possible sounds that can be produced by the double bass. Sounds that he has then been able to draw upon when when improvising or composing. Although at times it is clear that Dresser is well suited for his current role as a teacher of musical theory, he avoids the stodginess of some academics, and even provides a clear definition of just intonation by stating that “equal temperament divides an octave into 12 equal subdivisions, just intonation divides a fundamental frequency into an infinite number of equal subdivisions.” Other instances of remarkable insight and clarity can be found in his statements that the “violin was the electric guitar of its day,” and that “the brain best serves a musician when it is analyzing intuition,” an expression that he picked up from Ed Harkins. Throughout his talk Dresser illustrates all his points about intervals, harmonics, unique playing techniques, and the judicious use of amplification, by demonstrating them on his ever present double bass, while also answering all questions from the attentive and appreciative audience. Taken in its entirety this program serves as a telling testimony to the power of systematically analyzing the capabilities of an instrument, and the power and beauty that can be derived from a wedding of free improvisation with a thorough understanding of music theory.